2021MNRAS.506.3791R

Using the Lomb-Scargle periodogram and the weighted wavelet Z-transform techniques, we have searched for quasi-periodic oscillations (QPOs) of the BL Lacertae object (BL Lac), PKS J2134-0153, in the 15-GHz radio light curve announced by the Owens Valley Radio Observatory 40-m telescope during the period from 2008 January 5 to 2019 May 18. This is the first time that the search for periodic radio signals in the BL Lac PKS J2134-0153 has used these two methods, which consistently reveal a QPO of 4.69 ± 0.14 yr (>5σ confidence level). We discuss possible causes for this QPO, and we expect that the binary black hole scenario, where the QPO is caused by the precession of a binary black hole, is the most likely explanation. Thus, the BL Lac PKS J2134-0153 could be a good candidate for a binary black hole. In the binary black hole scenario, the distance between the primary black hole and the secondary black hole is a ∼ 1.83 x 10¹⁶ cm.